Hew Carrie M, Korakli Maher, Vogel Rudi F
Technische Mikrobiologie, Technische Universität München, Weihenstephaner Steig 16, D-85350 Freising, Germany.
Syst Appl Microbiol. 2007 Jun;30(4):257-67. doi: 10.1016/j.syapm.2006.08.002. Epub 2006 Sep 28.
Enterococci are ubiquitous organisms used to both improve the flavor and texture of fermented foods, and provide protective mechanisms as either a probiotic or antimicrobial additive. However, two species, E. faecalis and E. faecium, are also associated with 10% of nosocomial infections of the bloodstream, wounds, urinary tract and heart. While the genes involved in the pathogenicity of these organisms are slowly identified along with the mechanisms behind their regulation, the environmental signals involved in the conversion to pathogenicity remain unclear. The distribution of virulence genes was determined in 13 E. faecalis isolates from medical, food and animal sources. Regardless of their source of isolation, all isolates harbored between eight and thirteen virulence genes. Relative differences in expression of the virulence associated genes clpP, clpX, gls24, agg, efaA, gelE, and cylBL(L) were examined in E. faecalis TMW 2.63 and TMW 2.622 exposed to different environments (LB, BHI, respective supernatants, pig fecal extract, LB+6.5% NaCl, LB+pH5, LB+6.5% NaCl+pH5, and sausage medium) using RT-PCR and Lightcycler technology. Significant differences in expression were influenced by growth phase, environment, and isolate, which suggests that these three factors be taken into consideration during the selection of enterococci for use in foods or as probiotics rather than their source of isolation or set of virulence genes.
肠球菌是一种普遍存在的微生物，既用于改善发酵食品的风味和质地，又作为益生菌或抗菌添加剂提供保护机制。然而，粪肠球菌和屎肠球菌这两个菌种也与10%的血流、伤口、泌尿道和心脏医院感染有关。虽然这些生物体致病性相关的基因及其调控机制正在逐步被确定，但与致病性转变相关的环境信号仍不清楚。对从医疗、食品和动物来源分离出的13株粪肠球菌菌株的毒力基因分布进行了测定。无论分离来源如何，所有菌株都含有8至13个毒力基因。使用RT-PCR和Lightcycler技术，对暴露于不同环境（LB、BHI、各自的上清液、猪粪便提取物、LB+6.5%NaCl、LB+pH5、LB+6.5%NaCl+pH5和香肠培养基）的粪肠球菌TMW 2.63和TMW 2.622中与毒力相关的基因clpP、clpX、gls24、agg、efaA、gelE和cylBL(L)的表达相对差异进行了检测。表达的显著差异受生长阶段、环境和菌株的影响，这表明在选择用于食品或作为益生菌的肠球菌时，应考虑这三个因素，而不是其分离来源或毒力基因组合。
